U.S. patent application number 13/920723 was filed with the patent office on 2013-12-19 for power supply for led illumination.
The applicant listed for this patent is Sanken Electric Co., Ltd.. Invention is credited to Kengo Kimura, Hiroaki Kiuchi, Toshihiro Nakano, Yuji Sayama, Takayuki Yamashita.
Application Number | 20130334968 13/920723 |
Document ID | / |
Family ID | 49709006 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130334968 |
Kind Code |
A1 |
Nakano; Toshihiro ; et
al. |
December 19, 2013 |
Power Supply for LED Illumination
Abstract
An LED illumination system includes: a load including an LED
lamp; and a power supply device, the LED lamp configured to be
physically mounted on and demounted from the power supply device,
the power supply device comprising: a current feedback control
unit; a first voltage comparison unit configured to determine
whether the load is in a mounted state; a voltage feedback control
unit configured to decrease the voltage of the power supply device
to a safe voltage when demounting, and to increase the voltage of
the power supply device to perform the constant current control
when mounting; and a semiconductor switch element connected in
series between the load and the detection resistor, wherein the
mounted and demounted states of the load is detected by a voltage
of a main electrode of a high potential side of the semiconductor
switch element.
Inventors: |
Nakano; Toshihiro;
(Niiza-shi, JP) ; Kimura; Kengo; (Niiza-shi,
JP) ; Yamashita; Takayuki; (Niiza-shi, JP) ;
Sayama; Yuji; (Niiza-shi, JP) ; Kiuchi; Hiroaki;
(Niiza-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sanken Electric Co., Ltd. |
Niiza-shi |
|
JP |
|
|
Family ID: |
49709006 |
Appl. No.: |
13/920723 |
Filed: |
June 18, 2013 |
Current U.S.
Class: |
315/122 |
Current CPC
Class: |
Y02B 20/30 20130101;
H05B 45/48 20200101; H05B 45/37 20200101 |
Class at
Publication: |
315/122 |
International
Class: |
H05B 33/08 20060101
H05B033/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2012 |
JP |
2012-138027 |
Claims
1. An LED illumination system comprising a load including an LED
lamp, which includes at least one of LED rows having a plurality of
LED elements connected in series to each other, the LED rows being
connected in parallel to each other; and a power supply device that
supplies a direct current power to the load, the LED lamp
configured to be physically mounted on and demounted from the power
supply device, the power supply device comprising: a current
feedback control unit having a detection resistor to detect an
electric current flowing through the load, wherein the current
feedback control unit is configured to compare a value of the
electric current detected on the detection resistor with a
predetermined reference value, thereby performing a constant
current control; a first voltage comparison unit configured to
determine whether the load is in a demounted state, according to a
value of an output voltage of the power supply device; a voltage
feedback control unit configured to decrease the voltage of the
power supply device to a safe voltage when the load is demounted
from a mounted state, and to increase the voltage of the power
supply device to perform the constant current control when the load
is mounted from the demounted state; and a semiconductor switch
element connected in series between the load and the detection
resistor, wherein the mounted and demounted states of the load is
detected by a voltage of a main electrode of a high potential side
of the semiconductor switch element.
2. The LED illumination system according to claim 1, wherein the
first voltage comparison unit detects the output voltage of the
power supply device and compares the detected output voltage with a
fist reference voltage value, thereby outputting a signal, wherein
the power supply device further comprises: a second voltage
comparison unit configured to compare the voltage of the main
electrode of the high potential side of the semiconductor switch
element with a second reference voltage value, thereby outputting a
signal; and a logic circuit configured to be set by the signal of
the second voltage comparison unit and to be reset by the signal of
the first voltage comparison unit; wherein the logic circuit turns
the semiconductor switch element on while being set and turns the
semiconductor switch element off while being reset, and wherein the
logic circuit outputs a signal to decrease the output voltage of
the power supply device to the safe voltage, to the voltage
feedback control unit.
3. An LED illumination system comprising a load including an LED
lamp, which includes at least one of LED rows having a plurality of
LED elements connected in series to each other, the LED rows being
connected in parallel to each other and a power supply device that
supplies a direct current power to the load, the LED lamp
configured to be physically mounted on and demounted from the power
supply device, the power supply device comprising: a detection
resistor to detect an electric current flowing through the load; a
semiconductor element connected in series between the load and the
detection resistor; a current feedback control unit configured to
compare a value of the electric current detected on the detection
resistor with a predetermined reference value and to control a
control terminal of the semiconductor element based on an error
signal obtained by the comparison, thereby controlling the electric
current flowing through the load under a constant current control;
a power feedback control unit configured to detect a voltage of a
main electrode of the high potential side of the semiconductor
element, to compare the detected voltage value of the main
electrode of the high potential side with a predetermined reference
voltage, and to control the control terminal of the semiconductor
element based on an error signal obtained by the comparison,
thereby controlling the voltage of the main electrode of the high
potential side of the semiconductor element under a constant
voltage control; a first voltage comparison unit configured to
determine whether the load is in a demounted state, by comparing a
value of an output voltage of the power supply device with a first
reference voltage value, and then to transmit a demounting signal
when the load is demounted; and a voltage feedback controller
configured to decrease the voltage of the power supply device to a
safe voltage, based on the demounting signal from the first voltage
comparison unit.
4. The LED illumination system according to claim 3, wherein the
power supply device further comprises: a second voltage comparison
unit configured to detect the voltage of the main electrode of the
high potential side of the semiconductor element and to compare the
detected voltage value of the main electrode of the high potential
side with a second reference voltage value, thereby outputting a
signal; and a logic circuit configured to be set by the signal of
the second voltage comparison unit and to be reset by the
demounting signal from the first voltage comparison unit; wherein
the logic circuit turns the semiconductor element on while being
set and turns the semiconductor element off while being reset, and
wherein the logic circuit outputs a signal to decrease the output
voltage of the power supply device to the safe voltage, to the
voltage feedback control unit.
5. The LED illumination system according to claim 4, wherein, when
the load is mounted from the demounted state and then the logic
circuit is switched from the reset state to the set state, the
voltage feedback control unit increases the output voltage of the
power supply device so that the electric current flowing the load
can be controlled under a constant current control.
6. The LED illumination system according to claim 1, wherein the
load has a resistor connected in parallel to the LED rows.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Japanese Patent
Application No. 2012-138027 filed on Jun. 19, 2012, the entire
subject matter of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a power supply device able to
detect mounting and demounting of an LED lamp in an LED
illumination apparatus.
BACKGROUND
[0003] Recently, an illumination apparatus using white LEDs have
been commercialized as a replacement for existing fluorescent lamps
in a field of illumination. The LED illumination apparatuses have a
merit that a life span thereof is longer than the fluorescent
lamps. Also, because mercury is used in the fluorescent lamps, the
LED illumination apparatuses are favored in terms of environmental
burden.
[0004] In white LED illumination apparatuses, LED lamps are
typically driven by a step-down chopper type DC/DC converter or a
fly-back type DC/DC converter. For the LED lamps, a plurality of
LED elements are connected in series to each other, thereby
constantly keeping an electric current flowing through the LED
elements, reducing a brightness variation between each LED element,
and also ensuring a light intensity required for illumination.
[0005] Further, in a case of LED lamps requiring a higher light
intensity, a plurality of rows of LED elements, which are connected
in series to each other as described above, are connected in
parallel to each other to form an LED group, thereby ensuring a
higher light intensity.
[0006] However, although the LED illumination apparatuses have a
long lifetime as described above, the LED illumination apparatuses
have a finite life span of several ten thousand hours, and thus the
LED lamps have to be replaced after all. In addition, because the
LED lamps are configured by a plurality of LED elements connected
in series to each other, if only one of the plurality of LED
elements is disconnected/shorted, the LED lamps lose an
illumination function, or the electric current flowing through the
LED elements is increased, thereby shortening the life span.
[0007] To solve disconnection/short problems of the LED elements,
JP-A-H06-291732 discloses an LED apparatus including a plurality of
LED rows, each of which has a plurality of LED elements connected
in series to each other and are connected in parallel to each
other, and an electric current flowing through each LED group is
detected by a detection resistor, so that a disconnection is
detected based on decrease in voltage of the detection
resistor.
[0008] Further, JP-A-2008-258428 discloses an LED illumination
apparatus including an LED group having a plurality of LED rows
connected in parallel to each other, in which a circuit open state
is detected when an abnormality is occurred and thus any of LED
rows are disconnected, so that an electric current of magnitude
corresponding to LED rows having an abnormality is redistributed
over LED rows other than the disconnected LED rows.
SUMMARY
[0009] However, although a method for detecting whether or not the
LED rows are disconnected and also measures for suppressing
reduction of light intensity are disclosed in the related art,
there is no teaching with respect to replacement of the LED
lamp.
[0010] Namely, it is not considered that, according to abnormality
of the LED rows, the LED lamp is safely replaced with a normal LED
lamp without stopping electricity supply to the LED illumination
apparatus.
[0011] Accordingly, this disclosure provides at least an LED
illumination system in which an LED lamp can be safely replaced and
restored without stopping electricity supply to the LED
illumination apparatus.
[0012] In view of the above, an LED illumination system of this
disclosure comprises: a load including an LED lamp, which includes
at least one of LED rows having a plurality of LED elements
connected in series to each other, the LED rows being connected in
parallel to each other; and a power supply device that supplies a
direct current power to the load, the LED lamp configured to be
physically mounted on and demounted from the power supply device,
the power supply device comprising: a current feedback control unit
having a detection resistor to detect an electric current flowing
through the load, wherein the current feedback control unit is
configured to compare a value of the electric current detected on
the detection resistor with a predetermined reference value,
thereby performing a constant current control; a first voltage
comparison unit configured to determine whether the load is in a
demounted state, according to a value of an output voltage of the
power supply device; a voltage feedback control unit configured to
decrease the voltage of the power supply device to a safe voltage
when the load is demounted from a mounted state, and to increase
the voltage of the power supply device to perform the constant
current control when the load is mounted from the demounted state;
and a semiconductor switch element connected in series between the
load and the detection resistor, wherein the mounted and demounted
states of the load is detected by a voltage of a main electrode of
a high potential side of the semiconductor switch element.
[0013] According to the LED illumination system of this disclosure,
an LED lamp can be safely replaced and restored without stopping
electricity supply to the LED illumination system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The foregoing and additional features and characteristics of
this disclosure will become more apparent from the following
detailed descriptions considered with the reference to the
accompanying drawings, wherein:
[0015] FIG. 1 is a configuration view illustrating an LED
illumination apparatus according to a first aspect of this
disclosure;
[0016] FIG. 2 is a sequence diagram illustrating an operation of
each part when an LED lamp shown in FIG. 1 is mounted and
demounted;
[0017] FIG. 3 is a sequence diagram illustrating an operation of
each part until the LED lamp shown in FIG. 1 is mounted from a
demounted state;
[0018] FIG. 4 is a configuration view illustrating an LED
illumination apparatus according to a second aspect;
[0019] FIG. 5 is a sequence diagram illustrating an operation of
each part when an LED lamp shown in FIG. 4 is mounted and
demounted;
[0020] FIG. 6 is a sequence diagram illustrating an operation of
each part from a demounted state of the LED lamp shown in FIG. 4;
and
[0021] FIG. 7 is a circuit diagram illustrating a non-polarity LED
lamp by which electricity can be received independently of
polarity.
DETAILED DESCRIPTION
[0022] An LED illumination apparatus according to aspects of this
disclosure will be now described with reference to the accompanying
drawings. In the drawings, the same or similar components are
designated by the same or similar reference numerals.
[First Aspect]
[0023] FIG. 1 is a configuration view illustrating an LED
illumination apparatus according to a first aspect of this
disclosure.
[0024] With reference to FIG. 1, the configuration of the LED
illumination system 1 according to the present aspect will be
described. The LED illumination system 1 includes a direct current
power source E, a power supply device 2, and an LED lamps LEDS. A
voltage of the direct current power source E is converted to a
voltage driving the LED lamps LEDS by the power supply device 2,
and then supplied to the LED lamps LEDS through terminals TA1 and
TA2 of the power supply device 2. Although the power supply device
2 shown in FIG. 1 is configured as a fly-back type converter, the
power supply device 2 may be configured as a step-up or step-down
chopper type converter or the like, and the converter may also be
substituted by other types.
[0025] The LED lamp LEDS includes terminals TA1 and TA2 and has a
shape allowing for the LED lamp LEDS to be mounted and demounted as
a unitary assembly on and from the power supply device 2.
[0026] As shown in FIG. 1, the LED lamp LEDS receives electricity
in a polarity manner, in which the terminal TA1 has a plus polarity
and the terminal TA2 has a minus polarity. However, the LED lamp
LEDS may be replaced with a non-polarity LED lamp LEDS as shown in
FIG. 7.
[0027] The power supply device 2 shown in FIG. 1 is configured as a
fly-back type DC/DC converter, and has a series circuit of a
primary coil of a transformer T1 and a switching element M1
connected to the direct current power source E. A secondary circuit
of the transformer T1 is connected to a series circuit of a diode
D1 and a smoothing capacitor Co, and a voltage between both
terminals of the smoothing capacitor Co become an output voltage
outputted to the LED lamp LEDS.
[0028] Here, a negative electrode of the smoothing capacitor Co is
connected to GND, and a positive electrode of the smoothing
capacitor Co is connected to the terminal TA1. The terminal TA1 is
connected to a positive electrode of the LED lamp LEDS, and a
negative electrode of the LED lamp LEDS is connected to the
terminal TA2. The terminal TA2 is connected to GND through a series
circuit of a switching element M2 and a current detection resistor
R3.
[0029] In addition to the components described above, the fly-back
type DC/DC converter is configured by a comparator PWM-COMP, a
triangular wave oscillator OSC, a current feedback control unit and
a voltage feedback control unit, and additionally includes a first
voltage comparison unit, a second voltage comparison unit, a
flip-flop circuit FF1 and a switch SW1.
[0030] A gate of the switching element M1 of the fly-back type
DC/DC converter is connected with an output of the comparator
PWM-COMP configured to generate a switching pulse, which is a gate
driving signal, and an inverting terminal of the comparator
PWM-COMP is connected to the triangular wave oscillator OSC. One of
non-inverting terminals of the comparator PWM-COMP is connected to
an output terminal of an error amplifier OPcc, which becomes the
current feedback control unit. The other of the non-inverting
terminals is connected to an output terminal of an error amplifier
OPcv, which becomes the voltage feedback control unit. Here, the
comparator PWM-COMP determines a pulse width of the switching pulse
by comparing a triangular wave voltage from the triangular wave
oscillator OSC, which is connected to the inverting terminal, with
a signal voltage from any one of the current feedback control unit
and the voltage feedback control unit, which are connected to the
non-inverting terminals.
[0031] A non-inverting terminal of the error amplifier OPcc is
connected to a reference voltage Vrc, which becomes a reference
value of an electric current flowing through the LED lamp, and an
inverting terminal thereof is connected to a connection node
between the current detection resistor R3 and the switching element
M2.
[0032] Also, a non-inverting terminal of the error amplifier OPcv
is connected to a reference voltage Vry and an inverting terminal
thereof is connected to GND through a resistor R2 and also
connected to one of terminals of the switch SW1. The other terminal
of the switch SW1 is connected to the positive electrode of the
smoothing capacitor Co through a resistor R1 and also connected to
a non-inverting terminal of a voltage comparator CPre, which
constitutes the first voltage comparison unit. An inverting
terminal of the voltage comparator CPre is connected to a first
reference voltage Vrr.
[0033] The second voltage comparison unit is configured by a
voltage comparator CPat, a second reference voltage Vra and a
resistor R4. An inverting terminal of the voltage comparator CPat
is connected to the second reference voltage Vra, and a
non-inverting terminal thereof is connected to one of terminals of
the resistor R4 and a drain of the switching element M2. Also, the
resistor R4 is connected in parallel to a series circuit of the
switching element M2 and the current detection resistor R3, and the
other terminal of the resistor R4 is grounded to GND.
[0034] A setting terminal of the flip-flop FF1 is connected with an
output of the voltage comparator CPat of the second voltage
comparison unit, and a reset terminal thereof is connected with an
output of the voltage comparator CPre of the first voltage
comparison unit. A Q output of the flip-flop FF1 is connected to a
gate of the switching element M2 and a Qb (Q bar) output thereof is
connected to a control terminal of the switch SW1.
[0035] The LED illumination system 1 as shown in FIG. 1 detects
whether the LED lamp LEDS as a load is present or not, by the first
voltage comparison unit and the second voltage comparison unit. In
a state where the LED lamp LEDS is demounted, the first voltage
comparison unit detects a demounted state and then resets the
flip-flop FF1 and also turns the switch SW1 on, so that the voltage
feedback control unit decreases an output voltage of the power
supply device 2 to a safe voltage. As described above, the LED lamp
LEDS is LED rows in which a plurality of LED elements are connected
in series to each other, and thus a voltage of about 50 V to 100 V
is typically required. Therefore, when the LED lamp LEDS is
detached, a risk of electric shock has to be suppressed and thus
the voltage is decreased to a safe voltage (DC 42 V or lower). The
safe voltage can be set by a resistance ratio between the resistors
R1 and R2 and the reference voltage Vrv.
[0036] Also, when the LED lamp LEDS as a load is mounted, the
output voltage of the power supply device 2 is applied to the drain
of the switching element M2 through a resistor R5 of the LED lamp
LEDS. This is detected by the second voltage comparison unit and
then the flip-flop FF1 is set. Accordingly, the switching element
M2 is turned on and the switch SW1 is turned off, so that control
by the voltage feedback control unit is switched to control by the
current feedback control unit. In other words, the LED lamp LEDS is
connected with the output of the power supply device 2 through the
series circuit of the switching element M2 and the current
detection resistor R3, and the power supply device 2 is controlled
by the current feedback control unit so that an electric current
flowing through the LED lamp LEDS becomes a constant current.
[0037] FIG. 2 is a sequence diagram illustrating an operation of
each part when the LED lamp shown in FIG. 1 is mounted and
demounted. Also, FIG. 3 is a sequence diagram illustrating an
operation of each part from the demounted state of the LED lamp
shown in FIG. 1 to mounting thereof.
[0038] Next, with reference to FIGS. 2 and 3, an operation of each
part of the LED illumination system 1 according to the present
aspect will be described.
[0039] During times t0 to t3 as shown in FIG. 2, the LED lamp LEDS
is mounted on the power supply device 2. At the time t0, the direct
current power source E supplies power to the power supply device 2
and switching of the switching element M1 is started, and thus the
output voltage Vo starts to be increased.
[0040] When reaching the time t1, the non-inverting terminal of the
comparator CPat of the second voltage detection unit, which is
detecting a drain voltage of the switching element M2, exceeds the
second reference voltage Vra, and thus an H-leveled output signal
is inputted to the setting terminal of the flip-flop FF1. As a
result, the flip-flop FF1 is set, and thus an H-signal is outputted
from the Q output. This H-signal is applied to the gate of the
switching element M2, thereby turning the switching element M2 on.
Also, the Qb (Q bar) output is changed to an L-signal and as a
result, the switch SW1 is turned from on to off. Thus, a partial
voltage of the output voltage Vo due to the resistors R1 and R2,
which has been inputted to the inverting terminal of the error
amplifier OPcv of the voltage feedback control unit, is
disconnected, and the inverting terminal of the error amplifier
OPcv becomes a GND potential through the resistor R2. As a result,
the output voltage of the error amplifier OPcv outputs an H-signal
to the other non-inverting terminal of the comparator PWM-COMP,
thereby stopping a function of the voltage feedback control unit of
controlling the output voltage Vo.
[0041] Here, as the voltage feedback control unit is stopped, the
output voltage Vo is further increased over the times t1 to t2 and
then an electric current Io starts to flow in the LED lamp LEDS
through the series circuit of the switching element M2 and the
current detection resistor R3. At the time t2, when the electric
current Io flowing through the LED lamp LEDS reaches the current
reference value Vrc of the error amplifier OPcc of the current
feedback control unit, the output voltage of the error amplifier
OPcc is outputted to the one non-inverting terminal of the
comparator PWM-COMP so that a voltage value dropped by the current
detection resistor R3 is to be the same as a reference voltage
corresponding to the current reference value Vrc. As a result, the
electric current Io is controlled under a constant current
control.
[0042] At the time t3, if the LED lamp LEDS as a load is demounted,
the power supply device 2 becomes a no-load state and thus the
output voltage Vo is suddenly increased. Therefore, when the output
voltage Vo reaches the first reference voltage Vrr, an H-signal
from the output of the comparator CPre of the first voltage
comparison unit, which is detecting the output voltage Vo, is
inputted to the reset terminal of the flip-flop FF1, thereby
resetting the flip-flop FF1. As a result, the Qb output is inverted
such that an H-signal is outputted to the control terminal of the
switch SW1, thereby turning the switch SW1 on. Also, the Q output
outputs an L-signal, thereby turning the switching element M2 off.
Therefore, a partial voltage of the output voltage Vo due to the
resistors R1 and R2 is inputted to the inverting terminal of the
error amplifier OPcv of the voltage feedback control unit, and thus
a control for decreasing the output voltage Vo to a voltage value,
which is obtained by multiplying the resistance ratio between the
resistors R1 and R2 by the reference voltage Vrv, namely for
decreasing the output voltage Vo to the safe voltage, is started.
Then, the output voltage Vo reaches and keeps a stable voltage at a
time t4.
[0043] Also, at the time t3, since the LED lamp LEDS is demounted,
the electric current Io flowing through the current detection
resistor R3 becomes zero, and thus the inverting terminal of the
error amplifier OPcc of the current feedback control unit becomes
the GND potential through the current detection resistor R3.
Therefore, the output voltage of the error amplifier OPcc outputs
an H-signal to the one non-inverting terminal of the comparator
PWM-COMP, and thus a function of the current feedback control unit
of controlling the output current Io is stopped. In other words, at
the time t3, the output current Io control by the current feedback
control unit is switched to the voltage control by the voltage
feedback control unit.
[0044] At a time t5, if the LED lamp LEDS as a load is re-mounted,
the drain voltage of the switching element M2 becomes a partial
voltage of the output voltage Vo due to the resistor R5 and the
resistor R4 and exceeds a value of the second reference voltage
Vra. The non-inverting terminal of the comparator CPat of the
second voltage detection unit, which is detecting the drain voltage
of the switching element M2, exceeds the second reference voltage
Vra, and thus an H-leveled output signal is inputted to the setting
terminal of the flip-flop FF1. As a result, the flip-flop FF1 is
set, and thus an H-signal is outputted from the Q output. This
H-signal is applied to the gate of the switching element M2,
thereby turning the switching element M2 on. Also, the Qb (Q bar)
output is changed to an L-signal and thus the switch SW1 is turned
from on to off. Thus, a partial voltage of the output voltage Vo
due to the resistors R1 and R2, which has been inputted to the
inverting terminal of the error amplifier OPcv of the voltage
feedback control unit, is disconnected, and the inverting terminal
of the error amplifier OPcv becomes the GND potential through the
resistor R2. Then, the output voltage of the error amplifier OPcv
outputs an H-signal to the other non-inverting terminal of the
comparator PWM-COMP, thereby stopping a function of the output
voltage Vo control the voltage feedback control unit. Thus, the
output voltage Vo is increased, and the electric current Io starts
to flow in the LED lamp LEDS through the series circuit of the
switching element M2 and the current detection resistor R3.
[0045] At the time t6, when the electric current Io flowing through
the LED lamp LEDS reaches the current reference value Vrc of the
error amplifier OPcc of the current feedback control unit, the
output voltage of the error amplifier OPcc is outputted to the one
non-inverting terminal of the comparator PWM-COMP so that a voltage
value dropped by the current detection resistor R3 is to be the
same as a reference voltage corresponding to the current reference
value Vrc. As a result, the electric current Io is controlled under
a constant current control.
[0046] Next, FIG. 3 is a sequence diagram illustrating an operation
of each part when the direct current power source E supplies power
to the power supply device 2 in a state where the LED lamp is
demounted, and the description thereof is given below.
[0047] At a time t7, when the direct current power source E
supplies power to the power supply device 2, switching of the
switching element M1 is started, and thus the output voltage Vo
starts to be increased.
[0048] When reaching a time t8, because the LED lamp LEDS has not
been connected to the terminals TA1 and TA2, the non-inverting
terminal of the comparator CPat of the second voltage comparison
unit is not applied with a voltage and thus becomes the GND
potential through the resistor R4. Therefore, the flip-flop FF1
remains in a reset state, and then the switch SW1 keeps and an
on-state and the switching element M2 keeps an off-state. Also, an
inverting terminal voltage of the error amplifier OPcc of the
current feedback control unit becomes the GND potential through the
current detection resistor R3, and thus the function thereof is
stopped. In this case, because the switch SW1 is on, the error
amplifier OPcv of the voltage feedback control unit limits the
output voltage Vo to the safe voltage.
[0049] Then, at a time t9, if the LED lamp LEDS as a load is
mounted, the output voltage Vo is applied to the drain of the
switching element M2 through the resistor R5 via the terminals TA1
and TA2. The drain voltage of the switching element M2 becomes a
partial voltage of the output voltage Vo due to the resistor R5 and
the resistor R4 and exceeds a value of the second reference voltage
Vra. The non-inverting terminal of the comparator CPat of the
second voltage detection unit, which is detecting the drain voltage
of the switching element M2, exceeds the second reference voltage
Vra, and thus an H-leveled output signal is inputted to the setting
terminal of the flip-flop FF1. As a result, the flip-flop FF1 is
set, and thus an H-signal is outputted from the Q output. This
H-signal is applied to the gate of the switching element M2,
thereby turning the switching element M2 on. Also, the Qb (Q bar)
output is changed to an L-signal and as a result, the switch SW1 is
turned from on to off. Thus, a partial voltage of the output
voltage Vo due to the resistors R1 and R2, which has been inputted
to the inverting terminal of the error amplifier OPcv of the
voltage feedback control unit, is disconnected, and then the
inverting terminal of the error amplifier OPcv becomes the GND
potential through the resistor R2.
[0050] As a result, the output voltage of the error amplifier OPcv
outputs an H-signal to the other non-inverting terminal of the
comparator PWM-COMP, thereby stopping a function of the output
voltage Vo control of the voltage feedback control unit. The output
voltage Vo is increased, and then the electric current Io starts to
flow in the LED lamp LEDS through the series circuit of the
switching element M2 and the current detection resistor R3. Also,
the electric current Io flowing through the LED lamp LEDS is
controlled under a constant current control by the current feedback
control unit.
[0051] As described above, according to the LED illumination system
1 according of the present aspect, a replacement operation, in
which a failed LED lamp is demounted and then a normal LED lamp is
mounted, is to be safely performed without stopping electricity
supply to the LED illumination apparatus.
[Second Aspect]
[0052] FIG. 4 is a configuration view illustrating an LED
illumination apparatus according to a second aspect. In FIG. 4, the
components similar to those in FIG. 1 are designated by the same
reference numerals, and thus the description thereof is
omitted.
[0053] The LED illumination system la according to the second
aspect has a configuration, in which a dropper-type constant
current control unit is incorporated into the switching operation
of the switching element M2 of the first aspect. Namely, a voltage
between main electrodes of the switching element M2 is not used as
a saturated region, but is set to become an unsaturated region
causing a dropper operation, and also an electric current flowing
through the LED lamp LEDS is controlled under a constant current
control based on a voltage detected by the current detection
resistor R3 to become a constant current.
[0054] Meanwhile, a power feedback control unit is added instead of
the current feedback control unit of the first aspect, so that the
voltage between the main electrodes of the switching element M2
becomes a predetermined unsaturated voltage.
[0055] Also, a peripheral portion of a comparator PWM-COMPa of a
power supply device 2a is similar to the peripheral portion of the
comparator PWM-COMP of the first aspect, but it has a configuration
changed to an application employing a general comparator
(PWM-COMPa), in which the number of non-inverting terminals of the
comparator PWM-COMP is changed from two to one.
[0056] Specifically, as shown in FIG. 4, a non-inverting terminal
of the comparator PWM-COMPa is connected with anodes of diodes D2
and D3, and a cathode of the diode D3 is connected to the output of
the error amplifier OPcv of the voltage feedback control unit.
Also, a cathode of the diode D2 is connected to an output of an
error amplifier OPpw of the power feedback control unit. This
connection method is intended to control a non-inverting terminal
voltage of the comparator PWM-COMPa by electric currents inputted
from each error amplifier. A reference voltage Vrf as a bias source
is connected to the non-inverting terminal of the comparator
PWM-COMPa through a resistor R6.
[0057] Then, components of the second aspect different from those
in FIG. 1 illustrating the configuration of the first aspect will
be described in detail.
[0058] The dropper-type constant current control unit including the
switching element M2 is configured by an error amplifier OPcc, a
reference voltage Vrc, a switch SW2, a detection resistor R3, a
resistor R7 and a capacitor C3. A non-inverting terminal of the
error amplifier OPcc is connected to the reference voltage Vrc, and
an inverting terminal thereof is connected to a connection node
between a source of the switching element M2 and the detection
resistor R3 and is also connected to one of terminals of the
capacitor C3 and to one of terminals of the resistor R7. An output
terminal of the error amplifier OPcc is connected to one of
terminals of the switch SW2 and to the other terminal of the
capacitor C3, and the other terminal of the switch SW2 is connected
to a gate of the switching element M2 and the other terminal of the
resistor R7.
[0059] Also, the Q output of the flip-flop FF1 is connected to a
control terminal of the switch SW2. This is different in that, in
FIG. 1, the Q output of the flip-flop FF1 is connected to the gate
of the switching element M2.
[0060] The dropper-type constant current control unit including the
switching element M2 detects an electric current Io of the LED lamp
LEDS as a load on the detection resistor R3, compares the detected
voltage with the reference voltage Vrc by the error amplifier OPcc,
and then controls a gate voltage of the switching element M2
through the switch SW2 so that the detected voltage has the same
voltage value as that of the reference voltage Vrc. However, the
condition causing a constant current operation to be performed
requires that the Q output of the flip-flop FF1 is an H-level and
the switch SW2 is on.
[0061] The power feedback control unit is configured by an error
amplifier OPpw, a reference voltage Vrp, a capacitor C1 and the
diode D2. A non-inverting terminal of the error amplifier OPpw is
connected to the reference voltage Vrp, and an inverting terminal
thereof is connected to a drain of the switching element M2, a
non-inverting terminal of a comparator CPat of a second voltage
comparison unit and one of terminals of a resistor R4. An output
terminal of the error amplifier OPpw is connected to the
non-inverting terminal of the comparator PWM-COMPa through the
diode 2 as described above, and also the capacitor C1 is connected
between the output terminal and the inverting terminal of the error
OPpw.
[0062] A operation of the power feedback control unit is similar to
the current feedback control unit shown in FIG. 1, but it is
different in that, in FIG. 1, the electric current Io is controlled
to eliminate an error between the value detected on the resistor R3
and the reference voltage Vrc in FIG. 1, whereas, in FIG. 4, the
output voltage of the power supply device 2a is controlled to
eliminate an error between a drain voltage of the switching element
M2 and the reference voltage Vrp.
[0063] FIG. 5 is a sequence diagram illustrating an operation of
each part when the LED lamp shown in FIG. 4 is mounted and
demounted. Also, FIG. 6 is a sequence diagram illustrating an
operation of each part from a demounted state of the LED lamp shown
in FIG. 4.
[0064] Next, with reference to FIGS. 5 and 6, an operation of each
part of the LED illumination system la according to the second
aspect will be described.
[0065] During times t0 to t3 as shown in FIG. 5, the LED lamp LEDS
is mounted on the power supply device 2a. At the time t0, the
direct current power source E supplies to the power supply device
2a, and switching of the switching element M1 is started, and thus
the output voltage Vo starts to be increased. When reaching the
time t1, the non-inverting terminal of the comparator CPat of the
second voltage detection unit, which is detecting the drain voltage
of the switching element M2, exceeds the second reference voltage
Vra, and thus an H-leveled output signal is inputted to the setting
terminal of the flip-flop FF1. As a result, the flip-flop FF1 is
set, and thus an H-signal is outputted from the Q output. This
H-signal is applied to the control terminal of the switch SW2,
thereby turning the switch SW2 on. Therefore, although the constant
current control unit becomes an operating state, the output voltage
Vo does not reach a voltage causing an electric current to flow to
the LED lamp LEDS, and thus the electric current Io does not yet
flow at the time t1.
[0066] Also, the Qb (Q bar) output is changed to an L-signal, and
thus the switch SW1 is turned from on to off. Thus, a partial
voltage of the output voltage Vo due to the resistors R1 and R2,
which has been inputted to the inverting terminal of the error
amplifier OPcv of the voltage feedback control unit, is
disconnected and the inverting terminal of the error amplifier OPcv
becomes a GND potential through the resistor R2. As a result, the
output voltage of the error amplifier OPcv outputs an H-signal to
the cathode of the diode D3, thereby stopping a function of the
voltage feedback control unit of controlling the output voltage
Vo.
[0067] Here, as the voltage feedback control unit is stopped, the
output voltage Vo is further increased over the times t1 to t2, and
the electric current Io starts to flow in the LED lamp LEDS through
the series circuit of the switching element M2 and the detection
resistor R3. At the time t2, when the electric current Io flowing
through the LED lamp LEDS reaches the current reference value Vrc
of the error amplifier OPcc of the constant current control unit,
the error amplifier OPcc controls the gate voltage of the switching
element M2 through the switch SW2 so that a voltage value dropped
by the detection resistor R3 is to be the same as a reference
voltage corresponding to the current reference value Vrc. In
addition, immediately after the time t2, the power feedback control
unit controls the non-inverting terminal voltage of the comparator
PWM-COMPa so that the drain voltage of the switching element M2 has
a value similar to that of the reference voltage Vrp, thereby
controlling the output voltage Vo of the power supply device
2a.
[0068] At the time t3, if the LED lamp LEDS as a load is demounted,
the power supply device 2a becomes a no-load state, and thus the
output voltage Vo is suddenly increased. In this case, when the
output voltage Vo reaches the first reference voltage Vrr, an
H-signal from the output of the comparator CPre of the first
voltage comparison unit, which is detecting the output voltage Vo,
is inputted to the reset terminal of the flip-flop FF1, thereby
resetting the flip-flop FF1.
[0069] As a result, the Qb output is inverted such that an H-signal
is outputted to the control terminal of the switch SW1, thereby
turning the switch SW1 on. Also, the Q output outputs an L-signal,
thereby turning the switch SW2 off. Therefore, a partial voltage of
the output voltage Vo due to the resistors R1 and R2 is inputted to
the inverting terminal of the error amplifier OPcv of the voltage
feedback controller, and thus a control for decreasing the output
voltage Vo to a voltage value, which is obtained by multiplying the
resistance ratio between the resistors R1 and R2 by the reference
voltage Vrv, namely for decreasing the output voltage Vo to the
safe voltage, is started. Then, the output voltage Vo reaches and
keeps a stable voltage at a time t4.
[0070] In addition, at the time t3, because the switch SW2 is
turned off, the switching element M2 is also turned off and thus a
function of the output current Io control of the constant current
control unit is stopped. Also, as the switching element M2 is
turned off, an inverting terminal voltage of the power feedback
control unit becomes the GND potential through the resistor R4, and
thus the output voltage of the error amplifier OPpw outputs an
H-signal to the cathode of the diode D2. As a result, at the time
t3, the PWM control of the power supply device 2a is switched from
the control by the power feedback control unit to the voltage
control by the voltage feedback control unit.
[0071] At a time t5, if the LED lamp LEDS as a load is re-mounted,
the drain voltage of the switching element M2 becomes a partial
voltage of the output voltage Vo due to the resistor R5 and the
resistor R4 and exceeds a value of the second reference voltage
Vra. The non-inverting terminal of the comparator CPat of the
second voltage detection unit, which is detecting the drain voltage
of the switching element M2, exceeds the second reference voltage
Vra, and thus an H-leveled output signal is inputted to the setting
terminal of the flip-flop FF1. As a result, the flip-flop FF1 is
set, and thus an H-signal is outputted from the Q output. This
H-signal is applied to the control terminal of the switch SW2,
thereby turning the constant current control unit and the switching
element M2 on. Also, the Qb (Q bar) output is changed to an
L-signal and as a result, the switch SW1 is turned from on to off.
Thus, a partial voltage of the output voltage Vo due to the
resistors R1 and R2, which has been inputted to the inverting
terminal of the error amplifier OPcv of the voltage feedback
control unit, is disconnected and the inverting terminal of the
error amplifier OPcv becomes the GND potential through the resistor
R2. As a result, the output voltage of the error amplifier OPcv
outputs an H-signal to the cathode of the diode D3, thereby
stopping a function of the voltage feedback control unit of
controlling the output voltage Vo. The output voltage Vo is
increased and the electric current Io starts to flow in the LED
lamp LEDS through the series circuit of the switching element M2
and the current detection resistor R3.
[0072] At the time t6, when the electric current Io flowing through
the LED lamp LEDS reaches the current reference value Vrc of the
error amplifier OPcc of the constant current control unit, the
output of the error amplifier OPcc controls the gate voltage of the
switching element M2 through the switch SW2 so that a voltage value
dropped by the detection resistor R3 is to be the same as a
reference voltage corresponding to the current reference value Vrc,
and as a result, the electric current Io flowing through the LED
lamp LEDS is controlled under a constant current control. In
addition, similarly to those immediately after the time t2, the
power feedback control unit controls the non-inverting terminal
voltage of the comparator PWM-COMPa so that the drain voltage of
the switching element M2 has a value similar to that of the
reference voltage Vrp, thereby controlling the output voltage Vo of
the power supply device 2a.
[0073] Next, FIG. 6 is a sequence diagram illustrating an operation
of each part when the direct current power source E supplies power
to the power supply device 2a in a state where the LED lamp is
demounted, and the description thereof is given below.
[0074] At a time t7, when the direct current power source E
supplies power to the power supply device 2a, switching of the
switching element M1 is started, and thus the output voltage Vo
starts to be increased.
[0075] When reaching a time t8, because the LED lamp LEDS has not
been connected to the terminals TA1 and TA2, the non-inverting
terminal of the comparator CPat of the second voltage comparison
unit is not applied with a voltage and thus becomes the GND
potential through the resistor R4. Therefore, the flip-flop FF1
remains in a reset state, and the switch SW1 keeps an on state and
the switch SW2 and the switching element M2 keeps an off-state.
Also, the inverting terminal voltage of the error amplifier OPpw of
the power feedback control unit becomes the GND potential through
the detection resistor R4, and thus the function thereof is
stopped. In this case, because the switch SW1 is on, the error
amplifier OPcv of the voltage feedback control unit limits the
output voltage Vo to the safe voltage.
[0076] Then, at a time t9, if the LED lamp LEDS as a load is
mounted, the output voltage Vo is applied to the drain of the
switching element M2 through the terminals TA1 and TA2, i.e., the
resistor R5. The drain voltage of the switching element M2 becomes
a partial voltage of the output voltage Vo due to the resistor R5
and the resistor R4 and exceeds a value of the second reference
voltage Vra. The non-inverting terminal of the comparator CPat of
the second voltage detection unit, which is detecting the drain
voltage of the switching element M2, exceeds the second reference
voltage Vra, and thus an H-leveled output signal is inputted to the
setting terminal of the flip-flop FF1. As a result, the flip-flop
FF1 is set, and thus an H-signal is outputted from the Q output and
the switch SW2 is turned on. Also, the constant current control
unit starts to be operated and the switching element M2 is turned
on.
[0077] Also, the Qb (Q bar) output is changed to an L-signal and as
a result, the switch SW1 is turned from on to off. Thus, a partial
voltage of the output voltage Vo due to the resistors R1 and R2,
which has been inputted to the inverting terminal of the error
amplifier OPcv of the voltage feedback control unit, is
disconnected and the inverting terminal of the error amplifier OPcv
becomes the GND potential through the resistor R2. As a result, the
output voltage of the error amplifier OPcv outputs an H-signal to
the cathode of the diode D3, thereby stopping a function of the
voltage feedback control unit of controlling the output voltage Vo.
The output voltage Vo is further increased, and the electric
current Io starts to flow in the LED lamp LEDS through the series
circuit of the switching element M2 and the detection resistor R3.
At a time t10, the electric current Io flowing through the LED lamp
LEDS is controlled under a constant current control by the constant
current control unit. In addition, immediately after the time t10,
the voltage feedback control unit also starts to be operated, and
thus the power supply device 2a is controlled by the voltage
feedback control unit.
[0078] As described above, similarly to the first aspect, the LED
illumination system la according to the second aspect allows a
replacement operation, in which a failed LED lamp is demounted and
then a normal LED lamp is mounted, to be safely performed without
stopping electricity supply to the LED illumination apparatus.
[0079] In the foregoing, although examples of aspects of this
disclosure has been described, this disclosure is not limited to
the above specific aspects, and accordingly, various changes and
modifications thereof may be made within the scope of this
disclosure as defined by the appending claims. For example,
although the power supply device has been described using the
fly-back type DC/DC converter, the converter may be changed to a
forward type, or a step-up or step-down chopper-type.
[0080] In addition, the LED lamp LEDS as a load may be
appropriately changed to an LED lamp LEDSa shown in FIG. 7, by
which electricity can be received independently of polarity.
* * * * *